Valuing Land Using Wholesale Calculator

[Moshay Laren]

Hello BP! 

I have a contract on a parcel of land in a vastly developing community in South Philly. The purchase agreement is 100K. The lot is 643 sq ft. Other comparable lots in same area within (.1) mile are listed on the market for $79,990 - $123,500. New construction homes within (1) mile averaging between 1100-1600sqft with comparable lot size are selling between 300k-419K. 

1. Is it safe to average the cost to build a 1400sqft midlevel home between $100 - $120? Or is that too low

2. Is it ok to average the ARV (once the home is built) at 400K?

3. "Can I" or "how do" I use the wholesale calculator for this scenario? If not, what analysis vehicle would you recommend I use to show potential Cash Buyers the ROI?

Thank you in advance for you assist!